In the field of plasma physics, it is desirable to analyze the bahavior of a short light pulse whose spectra vary rapidly with time. In one application, for example, it is desirable to analyze the time behavior of a pulse of below 100 nanoseconds duration that is scattered by a time varying plasma to produce complex and variable spectra corresponding with certain important and rapidly changing plasma characteristics. Heretofore, however, this analysis has required spectrometers employing a plurality of separate and expensive photomultiplier tube light detectors and a plurality of separate and expensive oscilloscopes for each of a plurality of frequency channels of the incident light. Moreover, it has been a problem of no small significance to calibrate the various detectors and oscilloscopes.